DNA methyl transferase inhibiting halogenated monoterpenes from the Madagascar red marine alga Portieria hornemannii

Three new halogenated monoterpenes, 2, 3, and 4, along with the known compounds halomon ( 1) and two analogues, 5 and 6, were isolated from the Madagascar red marine alga Portieria hornemannii. The structures of all three new compounds were determined by NMR spectroscopy in combination with mass spectrometric data analysis. Two of these monoterpenes (1 and 2) were low micromolar inhibitors of DNA methyl transferase-1.